In general, a mobile communication system supports a handover for providing a seamless service, and a user terminal must have information about a handover target cell before the handover. In the 3rd Generation Partnership Project (3GPP) system, a user terminal can obtain information about a handover target cell before the handover by directly scanning neighbor cells in a periodic manner. In the Institute of Electrical and Electronics Engineers (IEEE) 802.16 system, a user terminal can obtain information about a handover target cell before the handover by receiving a neighbor list indicating information about neighbor BSs from a base station.
In the case of using the direct scanning operation, the user terminal does not obtain information about which neighbor BSs are present beforehand. In this case, the user terminal must scan all Frequency Allocations (FAs) and Cell_Idenfitiers (Cell_IDs) and must perform the scanning operation in a periodic manner, thus increasing the computational complexity of the user terminal.
In the case of using a neighbor list received from a base station, the user terminal scans only a base station included in the received neighbor list without the need to periodically scan neighbor BSs, thereby reducing the time required to perform the scanning operation.
However, the method based on the neighbor list cannot automatically update the neighbor list if the wireless channel environment of the base station changes due to the addition of neighbor BSs or FAs. Also, if a base station is initially omitted in generating a neighbor list, the user terminal cannot perform a handover to the omitted base station because the omission cannot be automatically corrected. If the base station generates and transmits a neighbor list, from which a neighbor BS is initially omitted, to the user terminal, it is impossible to perform an update on the omitted neighbor BS because the user terminal only scans base stations present in the neighbor list to report the scanning result to the base station.
There is, therefore, a need in the art for techniques to automatically update the neighbor list.